1. Hamner, Susan B. MSN, RN
  2. Morgan, Mary Elizabeth MSN, RN


The scope of services provided by the Staff Development Department or clinical educators in healthcare settings includes, but is not limited to, employee orientation, continuing education, and competency assessment. The critical issue of ascertaining competency of nursing staff in medication dosage calculation encompasses each of these functions. The authors describe the process of pilot testing a dosage calculation test in an ambulatory care setting, adapting it based on feedback, using it with orientees and current staff, and using the educational process with nurses needing assistance in dosage calculation.


Because the administration of medication is an important and frequent nursing function, and because it is one in which an error may cause dire patient outcomes, it is prudent for hospitals to assess the medication administration competency of nursing staff. A common practice in some hospitals across the nation is to administer some type of medication test to newly hired nurses during orientation as documentation of the nurses' competence in medication administration (Calliari, 1995). Other hospitals have elected not to administer a medication test, believing it to be a knowledge area and skill component inherent in obtaining the nursing license. Hospitals that do not give a medication test may use other forms of competency evaluation, such as nurses in a new organization working closely with a preceptor when giving medications.


Some nurses argue that because of the unit dose system, they are not called upon to calculate medication dosages and, therefore, should not be tested in this area. However, as with other skills that are used infrequently, the ability to perform correctly when the need arises may be in jeopardy. In Joint Commission terminology, this could be considered a "high-risk-low volume" skill. A study by Bayne and Bindler (1988) examined the ability of nurses to calculate medication dosages accurately. They found that only 35% of the sample set could perform medication calculation at the 90% proficiency level. They also found that nurses who had practiced for over 3 years scored lower than newer nurses. As a result of their findings, the authors advised healthcare institutions to evaluate the medication calculation skills of nurses periodically and to offer remedial programs as needed.


Calliari (1995) reported on a descriptive study performed to explore the relationship between medication test scores during orientation and reported medication errors. Prior to this study, the hospital's Nursing Education Service had considered eliminating the medication test in orientation. However, the results showed a significant association between those who failed the medication test and those who made medication errors (P <.03). Multiple regression analysis also showed a significant association between level of education and passing or failing and errors, but not between years of work experience. The nurses with more education were more likely to pass the test and less likely to make medication errors. As a result of this study, this hospital decided that valuable information was gained from the medication test and elected to continue using it. The author also pointed out that while the test was one for dosage calculation, most of the medication errors did not involve dosage calculation, but rather omission or transcription errors. Calliari postulated that "nurses who do well on calculation tests may have certain characteristics that make them more attentive to detail" (p. 14) making them less likely to make other types of medication errors as well.


Several studies found that dosage miscalculation was the second most common cause of medication error, following errors in time of administration (Bayne & Bindler, 1997). Bayne and Bindler (1997) stated that this was a problem that could be addressed by staff development educators. They studied whether medication calculation test scores differed when nurses' skills are enhanced either by computer-assisted instruction, self-study workbook, or group classroom instruction. They found that scores improved most for the classroom group, which was also the most expensive intervention.


One study took the concept a step further to determine the type of dosage calculation errors nurses were making-arithmetic operation errors or mathematical concept errors (Bliss-Holtz, 1994). This determination was made to plan for remediation strategies. The results confirmed that two types of errors were being made, as the passing rate (score of 85) was 72.5% when the participants used a calculator (indicating mathematical concept errors), and only 54.9% when a calculator was not used (indicating arithmetic errors). The author noted that there can be a cost-savings to the institution by diagnosing the types of errors being made.


Another hospital focused its efforts on providing education programs for nurses who had made medication errors (Werab, Alexander, Brunt, & Wester, 1994). The Staff Development Division created learning modules designed for one-on-one instruction that focused on oral, intramuscular and subcutaneous administration, intravenous administration, organizational skills, transcription, and dosage calculation. They also found that disorganization and difficulties with prioritization were contributing factors in medication errors, which they addressed in the learning modules as well. They received positive feedback from the participants using the modules, but also noted that it was a very time-consuming process for the staff-development educators. The review of the literature yielded no information on dosage calculation tests specific to ambulatory care areas.